Mapping offshore freshwater aquifers using marine controlled-source electromagnetics Canterbury Basin, New Zealand

Abstract

Offshore freshwater aquifers represent significant pathways for material transport across the coastal zone and have been proposed as an important agent in the geomorphic evolution of continental margins. However, the methods used to map the extent, volume, controls, and connectivity of offshore/onshore freshwater aquifers are still in the experimental phase. In this study, we present results from a series of marine controlled-source electromagnetic (CSEM) surveys performed in the Canterbury Basin, offshore the South Island of New Zealand. Nearly 300 km of marine CSEM data was collected using a newly developed seafloor-towed CSEM system that measures contrasts in the bulk electrical conductivity structure beneath the seafloor. Four surveys were collected across and/or in close proximity to IODP Expedition 317 Site U1353 in an area that contains a known shallow ( 50 m) freshwater anomaly.